Abstract

Construction of tree architectural databases over years is time
consuming and cannot easily capture event dynamics, especially when
both tree topology and geometry are considered. The present project
aimed to bring together models of topology and geometry in a single
simulation such that the architecture of an apple tree may emerge from
process interactions. This integration was performed using L-systems.
A mixed approach was developed based on stochastic models to simulate
plant topology and mechanistic model for the geometry. The succession
of growth units (GUs) along axes and their branching structure were
jointly modelled by a hierarchical hidden Markov model. A
biomechanical model, derived from previous studies, was used to
calculate stem form at the metamer scale, taking into account the
intra-year dynamics of primary, secondary and fruit growth. Outputs
consist of 3-D mock-ups - geometric models representing the
progression of tree form over time. To asses these models, a
sensitivity analysis was performed and descriptors were compared
between simulated and digitised trees, including the total number of
GUs in the entire tree, descriptors of shoot geometry (basal diameter,
length), and descriptors of axis geometry (inclination, curvature). In
conclusion, despite some limitations, MAppleT constitutes a useful
tool for simulating development of apple trees in interaction with
gravity.